Oval loudspeaker basket and method of manufacturing same

ABSTRACT

A METHOD OF MANUFACTURING AN OVAL LOUDSPEAKER BASKET EMPLOYING EXPANDED METAL TECHNIQUES. A FLAT BLANK OF MATERIAL IS PIERCED (E.G. PUNCHED) TO FORM A CENTRAL ANNULAR REGION, A PERIPHERAL OVAL FLANGE AND A NETWORK OF CONCENTRIC WEBS, RADIAL INTERCONNECTING WEBS AND CONCENTRIC SLOTS. THE ANNULAR PORTION IS DISPLACED FROM THE PERIPHERAL PORTION BETWEEN A PAIR OF DIE MEMBERS, EXPANDING THE WEBS TO FORM GENERALLY DIAMOND-SHAPED OPENINGS IN THE EXPANDED BASKET.

Nov. 9, 1971 A. L. COEN Original Filed June 5. 1967 5 Sheets-Sheet lINVENTUW moo L. 605M mm m A. L. COEN Nov, 9, 1971 OVAL LOUDSPEAKERBASKET AND METHOD OF MANUFACTURING SAME 5 Sheets-Sheet 2 Original FiledJune 5, 1967 HVWEWTflW 4.400 1. Com

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OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAME Original FiledJune 5, 1967 5 Sheets-Sheet 4 TQM n F? mm M E ii W Cam Nova 9, 1971 A.L... GOEN OVAL LOUDSPEAKER BASKET AND METHOD OF MANUFACTURING SAMEOriginal Filed June 5, 1967 5 Sheets-Sheet 5 3,618,185 OVAL LOUDSPEAKERBASKET AND METHOD OF MANUFACTURIING SAME Aldo L. Coen, Chicago, 1111.,assignor to RCA Corporation Original application June 5, 1967, Ser. No.643,473, new Patent No. 3,497,928. Divided and this application Feb. 12,1969, Ser. No. 810,075

lint. Cl. BZId 31/04 U.. C]. 29-61 4 Claims AlBfiTRACT (IF THEDKSCLOSURE A method of manufacturing an oval loudspeaker basketemploying expanded metal techniques. A flat blank of material is pierced(e.g. punched) to form a central annular region, a peripheral ovalflange and a network of concentric webs, radial interconnecting webs andconcentric slots. The annular portion is displaced from the peripheralportion between a pair of die members, expanding the webs to formgenerally diamond-shaped openings in the expanded basket.

This is a division of application Ser. N0. 643,473, filed June 5, 1967now Pat. No. 3,497,928.

This invention relates to loudspeakers and, more particularly isconcerned with a support structure or basket for supporting thediaphragm and magnet assembly of a loudspeaker and a method ofmanufacturing such a basket.

Generally, loudspeaker baskets are made by punching a blank from a sheetof metal (e.g. steel) and then forming the blank into a basket shapebetween a pair of dies. The blank is punched so as to provide, in theformed speaker basket, a central annular plateau region for mounting ofa voice coil and magnet assembly and a peripheral flange for attachingthe outer edge of the speaker cone or diaphragm to the basket and forattaching the entire assembly to a speaker enclosure. Sufficientmaterial is punched from the sheet of material so as to leave betweenthe central annual region and the periphery of the blank generallyradial ribs separated by substantial open spaces. The outside dimensionsof the blank are substantially greater than the outside dimensions ofthe finished basket. During the forming process, the edge of the blankis restrained but not clamped tightly so that as the central annularregion is displaced perpendicularly from the plane of the edge portionof the basket, metal from the edge portion is permitted to slip" towardsthe center and, at the same time, the radial ribs are stretchedslightly, the combined effect of edge slipping and rib stretchingproviding the total required displacement of the central annular regionfrom the peripheral flange. In such a construction, the initial size ofthe blank must be substantially greater than the outside dimension ofthe finished basket in order to accomplish the required displacement.

In accordance with the present invention, speaker baskets aremanufactured utilizing expanded metal techniques which are substantiallymore economical of metal than the prior method. In the expanded metalmethod, the outside dimensions of the starting blank for a given sizebasket are only slightly larger than the outside dimensions of thefinished basket and substantially smaller than the blank for the samesize basket manufactured by the former method.

It is a particular object of the present invention to provide an ovalloudspeaker basket (i.e. a basket for supporting a diaphragm having anoval outer periphery) manufactured by expanded metal techniques.

3,618,185 Patented Nov. 9, 1971 It is a further object of the presentinvention to provide a method for producing an oval expanded metalloudspeaker basket.

In accordance with the present invention, a method of forming a supportstructure for a loudspeaker assembly comprises the steps of piercing asheet of mechanically deformable material to provide, within an ovalboundary, a central annular ring, a plurality of closely spacedconcentric webs of substantial linear dimension disposed between thering and the oval boundary and interconnecting radial Web portionsinterconnecting each concentric web alternately with adjacent inner andouter ones of the concentric Webs, the radial and concentric websdefining concentric apertures having a linear dimension less than thatof the concentric webs but substantially greater than that of the radialwebs, rigidly clamping the edge portion of the pierced sheet outside theoval boundary, and displacing the annular ring along an axissubstantially perpendicular to the plane of the edge portion whileconforming the concentric and radial. webs to a substantially smoothsurface defined at one extreme by the oval boundary and defined at theopposite extreme by the annular ring for expanding the pierced sheet toform a loudspeaker basket.

In accordance with a further aspect of the present invention, a supportstructure for a loudspeaker assembly comprises an annular centralportion, an oval peripheral flange, the oval flange having associatedmajor and minor axes, and an apertured transition portion extendingbetween the oval flange and the central portion, the transition portioncomprising a network of relatively long, generally circumferential websand relatively short interconnecting radial webs, a plurality of thelong webs extending across the major axis and linking together segmentsof the oval flange disposed on each side of the major axis in adjacentquadrants of the oval.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation asWell as additional objects thereof will best be understood from thefollowing description when read in connection with the accompanyingdrawing in which:

FIG. 1 is a partial top view of an oval expanded metal loudspeakersupport structure or basket constructed in accordance with the presentinvention.

FIG. 2 is a front view, partially in section, of the support structureshown in FIG. 1.

FIG. 3 is a top view of a punched blank utilized for producing thestructure shown in FIGS. 1 and 2. 1

FIG. 4 is a diagrammatic sectional view taken through a punch pressshowing a step in the manufacture of the structure of FIGS. 1 and 2.

FIG. 5 is a diagrammatic sectional view taken through a forming pressshowing a further step in the manufacture of the structure of FIGS. 1and 2.

Referring now to FIGS. 1 and 2 of the drawing, the loudspeaker assemblycomprises a magnet structure 10 mounted upon a central annular,plateau-like portion 12 of a speaker basket indicated generally by thereference numeral 14. A cylindrical voice coil assembly 16 is mounted bymeans of a flexible suspension member 18 within a circular opening 20 inannular portion 12. Voice coil assembly 16 extends adjacent magnetstructure 10 and is coupled by means of an electrical lead wire assembly22 to a terminal board 24 mounted adjacent a barrel-shaped accessopening 26a in basket 14. A similar opening 26b is provideddiametrically opposite opening 26a adjacent annular portion 12. A dustcap 28 is provided over the exposed end of voice coil assembly 16. Aspeaker cone or diaphragm 310 having a central circular edge 30a and aperipheral oval edge 30b (i.e. an oval cone) is suspended between voicecoil assembly 16 and a second suspension member 32. Suspension member 32is retained within a peripheral flange 34 by means of a gasket 36 and isfastened by means of a suitable adhesive against a lip 38. Mountingholes 40 are provided in the lip between flange 34 and an oval boundary42 of basket 14. Central annular portion 12, lip 38, flange 34, and thetransition portion 14a of basket 14 all are formed from a unitary pieceof metal such as steel or other suitable material.

The central annular portion 12 of basket 14 is displayed from the planeof lip 38 along an axis which is perpendicular to that plane (see FIG.2). Annular portion 12 and lip 38 are joined together by transitionportion 14a which comprises a plurality of relatively long generallycircumferential webs 44 joined together by relatively shortinterconnecting radial web portions 46. Webs 44 and interconnectingradial web portions 46 define a plurality of apertures 48 which aregenerally diamond-shaped along the major and minor axes of basket 14 butare irregularly shaped at points intermediate those axes. The outermostends of the outermost ones of apertures 48 lie along the oval boundary42. Stated differently, the webs 44 which extend across the major axisof basket 14 are joined together to form continuous links between theportion of oval boundary 42 on one side of the major axis and theportion of oval boundary 42 on the other side of the major axis.

Furthermore, it should be noted that while the radial webs 46 which liealong the major and minor axes of oval flange 34 are radially aligned,the radial webs 46 between such axes are not radially aligned. Thepositioning of the radial webs is selected so as to provide a length foreach segment of the long webs 44 suflicient to provide the necessarydeformation thereof without fracturing. It has been found, for example,in the illustrated structure that a maximum permissible angle betweentwo segments of webs 44 meeting at a common radial web 46 isapproximately sixty degrees.

The manner in which the basket 14 is manufactured now will be describedreferring initially to FIG. 4. In FIG. 4, there is shown a sectionalview through a portion of a punch press designated generally by thereference numeral 458. The principal parts of the press 458 for purposesof this description consist of a stationary apertured base plate 460 anda reciprocating head 462 having a plurality of curved punches 464, thepunches 464 lying along concentric circles. Apertures 448 are providedin base plate 460 for receiving the punches 464 as head 462 is loweredand for permitting removal of material from a fiat strip of sheet metal450 which is placed upon base plate 460 for punching. In practice, sheetmetal 450 may be fed from a roll across base plate 460 from right toleft in FIG. 4 against an indexing stop (not shown) located at the leftend of base plate 460. When the sheet metal 450 contacts the indexingstop, head 462 is brought rapidly downward such that punches 464 producea predetermined plurality of apertures in sheet metal 450.

Where a large number of closely spaced apertures are required in thesheet 450, the punching operation preferably is carried out utilizing amulti-station punch press. For example, two separate heads, eachcontaining onehalf the required punches (i.e. alternate rows of therequired punches) and two separate base plates, each containing one-halfthe required apertures, may be provided in a single machine. In thatcase, as the sheet material 450 is fed into the press, the firstpunching operation will result in half the required apertures beingpunched in a first blank. The sheet 450 is then advanced and the secondpunching operation will result in a simultaneous punching of the secondhalf (i.e. the alternate rows) of the required apertures in the firstblank and the first half of the apertures being punched in a secondblank. In this manner, one blank will be completed for each punchingoperation 4 after the first one. On the third punching sequence, acutoff device may be provided for cutting off the first blank which nowpasses out of the punch press. 'In such an arrangement, the tools(punches and base plate) more readily may be fabricated.

Referring to FIG. 3, a flat punched blank 50 is shown which is producedin the manner described in connection with FIG. 4. The punched blank 50is utilized, in accordance with the present invention, for forming thebasket 14 shown in FIGS. 1 and 2. In FIG. 3, elements of the blank 50prior to forming which correspond to elements of the basket 14 (FIG. 1)after forming are indicated by the same reference numerals as are usedin FIGS. 1 and 2 with the addition of a prime notation following thenumerals in FIG. 3.

As shown in FIG. 3, the blank 50 from which basket 14 is formedcomprises a generally octagonal sheet of, for example, one thirty-secondinch thick steel of aluminum killed grade. A plurality of discontinuousconcentric apertures 48', a central circular pilot aperture 52 and apair ofmodified rectangular apertures 26a and 26b having curved ends(preferably segments of concentric circles) and straight sides arepunched in the sheet material. Continuous concentric webs 44' bounded atthe inside by annular portion 12', at the outside by an oval boundary42' (shown in dotted lines) and interrupted by apertures 26a and 26b areformed as a result of the punching. Webs 44' are joined together byinterconnecting radial web portions 46' which extend between adjacentapertures 48'. Central aperture 52 and two relatively small apertures 54and 56 lying along the major axis of blank 50 serve as pilot holes forpositioning blank 50 during the forming process as will be describedbelow.

Referring to FIG. 5, the manner in which punched blank 50 (FIG. 3) isformed into basket 14 (FIGS. 1 and 2) now will be described. 'In FIG. 5,there is shown a sectional view through a portion of a forming pressdesignated generally by the reference number 510. For purposes of thisdescription, the principal parts of forming press 510 consist of astationary base plate 512 including a male basket-forming die 514. Afloating ring 516 supported on an air cushion encircles the uppermostplateau region 518 of male die 514. Ring 516 is coupled by means ofsupporting pins 520 to a piston assembly 522 which extends within an air(or other hydraulic) cylinder 524. Pressure is maintained withincylinder 524 by means of a conventional pressurized air supply 526.

The forming press 510 further comprises a movable female basket-formingdie 530 and driving means (not shown) coupled to the female die 530 forreciprocating female die 530 along a vertical axis.

The punched blank 50 (shown in FIG. 3) is located upon plateau region518 and floating ring 516 by indexing means (e.g. pin 528) for forming.

In the operation of forming press 510, base plate 512 and male die 514remain stationary. Punched blank 50 is located on floating ring 516 andplateau region 518. Female die 530 is then moved vertically downwardsuch that initial contact is made between female die 530 and blank 50along the edge of blank 50 which rests on ring 516. The air pressureprovided by supply 526 (e.g. 80. p.s.i.) is selected such that the edgeof blank 50 is clamped between ring 516 and die 530 and thereby issubstantially restrained from sideways movement. As female die 530 isadvanced downwardly, the webs 44' and 46" of punched blank 50 (see FIG.3) are displaced and the apertures 48 between webs 44' are enlarged,thereby expanding blank 50 into the desired basket shape (see FIG. 1).Female die 530 is then lifted permitting removal of the formed basket.The dimensions of ring 516, rods 520 and dies 514 and 530 are arrangedsuch that the interconnecting webs 44 and 46 of the finished basket alllie along the smooth surfaces of the dies 514 and 530.

After removal from the forming press 510, the formed basket is trimmedalong its outer edge and mounting holes 40 (FIG. 1) and the largercentral voice coil hole 20 are punched by means of a conventionalvertical punch press. In the final trimming operation, only a verynarrow strip of material is discarded since, as was mentioned above theoutside dimensions of blank 50 are only slightly greater than theoutside dimensions of finished basket 14. The increase in the dimensionsalong the surface of transition portion 14a required to permit verticaldisplacement of annular portion 12 from lip 38 is provided substantiallysolely by the rearrangement of the webs 44 and 46 during the forming orexpansion operation. In a typical 8 x 12" oval basket, the savings inmaterial realized by virtue of the present invention is of the order oftwenty percent.

It should also be noted that, while the transition portion 14a of basket14 extends between a circular inner portion 12 and an oval outerboundary 42, the apertures 43 and the Webs 44 (FIG. 3) in the blank 50all lie on concentric circles. Such an arrrangement permits relativelysimple and therefore not excessively costly manufactun ing of thetooling (i.e. punches 464 and apertured base plate 460 of punch press458) required for producing the punched blank 50.

What is claimed is: 1. A method of forming a support structure for aloudspeaker assembly comprising the steps of piercing a fiat sheet ofmechanically deformable material to provide, within an oval boundaryhaving associated major and minor axes, a central annular ring, aplurality of closely spaced concentric webs of substantialcircumferential dimension disposed between said ring and said ovalboundary and radial web portions interconnecting each said concentricweb alternately with adjacent inner and outer ones of said concentricWebs, at least some of said concentric Webs terminating at said ovalboundary between said major and minor axes, said radial and concentricwebs defining concentric apertures having a circumferential dimensionless than that of said concentric Webs but substantially greater thanthat of said radial webs, rigidly clamping the edge portion of saidpierced sheet outside said oval boundary, and displacing said annularring along an axis substantially perpendicular to the plane of said edgeportion while conforming said concentric and radial webs to asubstantially smooth surface defined at one extreme by said ovalboundary and defined at the opposite extreme by said annular ring forexpanding said pierced sheet to form a loudspeaker basket.

2. A method of forming a support structure for a loudspeaker assemblyaccording to claim 1 wherein said radial Web portions being radiallyaligned along said axes and being radially mis-aligned intermediate saidaxes to provide sufiicient length for said concentric webs intermediatesaid axes to prevent fracture thereof upon displacement of said annularring.

3. A method according to claim 2 and further comprising piercing saidsheet of material to form at least a first access opening disposedadjacent said annular ring along said major axis, said access openingbeing defined by first and second side ribs and an end rib.

4. A method according to claim 3 wherein said radial webs intermediatesaid major and minor axes are dis placed from each other and from saidaccess opening ribs such that each segment of each said concentric webbetween adjacent inner and outer radial webs is of sufiicient length toprevent fracture upon deformation.

References Cited UNITED STATES PATENTS 865,173 9/1907 Eichberg 296.2. X1,144,668 6/1915 Rizzardi 2962 1,287,298 12/1918 Halvorson et al. 2401022,895,578 2/1946 Perganoe 40-1241 3,497,928 3/1970 Coen 296.1

FOREIGN PATENTS 767,336 1/1934 France 29163.5

JOHN F. CAMPBELL, Primary Examiner R. J. CRAIG, Assistant Examiner US.Cl. X.R. 296.2, 163.5

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. ,185Dated November 71 Inventor (x) Aldo L. Coen It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 1, line 42, that portion reading "annual" should read annularColumn 2, lines 25-36, that portion should be deleted. Column 3, line12, that portion reading "displayed" should read displaced Signed andsealed this 18th day of July 1972.

(SEAL) ttest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-lOSCI [10-69] USCOMM- 99 75.;159

ll 5v GOVERNMENT HUNTING OFFICE: 1," O'lC-L\l

